Okay, let's have a picture in here.
Motivation is not key source in doing a job, just as recreation does not involve restoration of work-related motivation. Motivation has bigger part at the employee, and smaller part at employer/manager. Both sides are stakeholders. At interview it is a plus if the applicant is highly motivated, but if he can do the job, he will be still a valued asset for the company.
Finishing a job, task, project late means difficulties. It needs a good understanding of processes, observation, people skills to do a good snapshot analysis to find blockages, rough points, and must be aware that the team is always having a momentum. Any low or high it is, their performance is a dynamicly changing output to better or worse direction. Reasoning with lack of motivation is an excuse. Without a doubt. It still does not mean it is by bad intention. If project issues are typically from a category, which never gets Action Point, none of the stakeholders do anything about it, or existing without resolution or workaround, but bothering the workers, it will generate frustration, and who does not quit, will be worn.
Suggestion: Go with them, get a picture what they are doing (and how), measure with good sense if it's ok by the standard that the company keeps, and if not, drive changes. Change people, habits, environment, tools, energy of the place,...or even the standard. If you are positive about that you provide them the minimum reasonable, optimally decent environment, and they show no performance change, it is time for discipline and regulations. Then change of people.